Cannabis dependence is a major public health problem. Treatments are of limited efficacy and one reason may be the failure to address the symptoms of cannabis withdrawal, such as negative affect and sleep disturbance, which may be associated with relapse to use. The purpose of this early Phase II developmental proposal is to explore the efficacy of the novel anticonvulsant drug gabapentin (Neurontin) for reducing cannabis withdrawal severity, facilitating abstinence, and reducing risk and severity of relapse in outpatients with cannabis dependence. Gabapentin appears to act on both GABA and glutamate systems to reduce CNS excitability. Clinical reports support the efficacy and safety of gabapentin in treatment of depression, anxiety, insomnia, and aggression. A medication with efficacy for the negative affect and sleep disturbances often associated with cannabis withdrawal is of significant interest as a potential pharmacotherapy for this disorder. The overall hypothesis under test is that gabapentin will improve symptoms of cannabis withdrawal, and as a result, facilitate setting a quit date, promote longer-term abstinence, and decrease risk and severity of relapse to cannabis use. Subjects will be 50 outpatients with current DSM IV cannabis dependence randomized to a 12-week, double-blind, placebo-controlled trial of gabapentin 1200 mg/d. Concomitantly, all subjects will receive motivation enhancement therapy (Visits 0-3) to facilitate a Week 4 cannabis quit date, and cognitive behavioral therapy (Visits 4-12) to prevent relapse. Post-treatment assessments will occur at Week 13. It is hypothesized that administration of gabapentin will result in significantly decreased cannabis withdrawal severity and that cannabis withdrawal severity will have a significant relationship with Week 4 cannabis quit rates and subsequent cannabis use. Results will provide information about the efficacy of gabapentin for reducing cannabis withdrawal severity and increasing cannabis quit rates, and the relationship between cannabis withdrawal severity and relapse to cannabis use. [unreadable] [unreadable]